A number of networks are moving towards a connection-oriented arrangement. An example of a connection oriented technology is Asynchronous Transfer Mode (ATM). Another example of a proposed technology that includes a connection-oriented (or channel based) capability is know as the Virtual Interface (VI) architecture, described in the Virtual Interface (VI) Architecture Specification, Version 1.0, Dec. 16, 1997, jointly authored by Compaq Corp., Intel Corp. and Microsoft Corp. While connection oriented technologies offer many advantages, in many instances it is desirable to maintain an interoperability between an existing connectionless technology and the connection-oriented technology. It is also desirable to maintain such interoperability, for example, when transitioning from a connectionless technology to a connection-oriented technology (or network) to allow some existing software and components to be used. The IEEE 802.3 Ethernet Local Area Network (LAN) standard is an example of a common connectionless technology or network.
Current approaches to provide LAN emulation over a connection-oriented network (such as ATM) have a number of disadvantages. One example is Asynchronous Transfer Mode (ATM) LAN Emulation, which is a specification provided by the ATM Forum for the coexistence of legacy LANs and ATM LANs, known as ATM LAN emulation. ATM Forum, “LAN Emulation Over ATM Specification,” Version 1.0, 1995. The ATM LAN Emulation specification is discussed in William Stallings, “Data and Computer Communications,” pp. 487-495, Fifth Edition, 1997.
As described in Stallings, the ATM LAN Emulation specification proposes the use of a centralized LAN Emulation Service (LES) to perform basic LAN emulation services for nodes in a network, including: to set up connections, to map MAC addresses to ATM addresses. The LES also includes a broadcast and unknown server (BUS) service to provide a broadcast/multicast a packet to plural nodes upon request from a client, and to provide a specialized protocol to allow nodes to learn ATM addresses of other nodes (i.e., by sending a LE_ARP_Request message).
There are a number of disadvantages of such a system. First, by using a centralized LES service, the network is prone to a single point of failure. Furthermore, the ATM LAN Emulation described above requires a separate and specialized address resolution protocol (ARP) protocol which is not compatible with the legacy or existing LAN networks in order to obtain the ATM address of a node corresponding to the node's MAC or LAN address. Moreover, calls through the operating system (OS) kernel requiring multiple buffer copies of data is typically required in many such existing computer systems, which can burden a processor with substantial overhead.